Ultrathin　Bi4Ti3O12　nanosheets　(NS)　with　the　thickness　about　3.9　nm　were　successfully　synthesized　by　a　hydrothermal　method　and　were　used　as　a　photocatalyst　for　the　oxidation　of　benzyl　alcohol　(BA)　to　benzaldehyde　(BAD).　The　photocatalytic　performance　of　NS　is　about　8　times　higher　than　that　of　bulk　Bi4Ti3O12.　In-situ　FTIR　of　pyridine　adsorption　and　NH3-TPD　reveal　that　NS　has　more　surface　Lewis　acid　sites　(Ti4+)　for　the　adsorption　and　activation　of　BA.　The　photogenerated　electrons　(e-)　and　holes　(h+)　of　NS　can　be　fully　used　to　produce　the　superoxide　radicals　and　carbon-centered　radicals,　respectively.　The　monolayer　nanosheet　structure　of　NS　not　only　greatly　promotes　the　separation　of　photogenerated　carriers,　but　also　achieves　the　efficient　activation　of　BA　molecules　via　the　C–OTi　coordination.　This　work　successfully　reveals　the　surface/interface　interactions　between　the　surface　active　sites　of　a　photocatalyst　and　the　reactive　molecules　via　using　ultrathin　nanosheet　as　a　molecular　platform.　©　2021　Elsevier　Inc.